Many materials, such as plastics, wood chips, grain, shredded garbage, particulate-form products, and like divided materials, are handled in materials handling equipment using rotary air-lock meters or rotary feeders. For example, the divided material may be fed to other solids handling equipment, such as mixers, blenders, or process vessels of various types. To prevent the escape of pressurized gas out, or air into a conveying line or other processing device, the divided material may be fed into the conveying line or to other systems by means of a rotary air-lock device. Other applications may use a rotary feeder to meter the flow of material.
Typically, such devices comprise a top inlet over a cylindrical housing, and a bottom outlet. Mounted in the housing is a rotor comprising a plurality of blades adapted to engage the periphery of the housing and to form with the housing as they rotate sealed chambers for conveying material from an inlet to the outlet. In many systems, the divided materials are fed by gravity into the upper portion of the feeder. In some designs, the upper edge of the housing is provided with a shearing surface that, with the edge of a rotor blade, forms a shear to cut off material projecting beyond the edge of a rotor blade as it rotates beneath the surface.
In some systems, the rotary air-lock feeder feeds a combination of particulate material and oversized material to pneumatic conveying systems, where the combination of materials are transported to other materials processing equipment, or may drop the combination of particulate material and oversized material into a gravity flow material processing system.
In some processes, it may be necessary to remove oversize material from the divided particulate material before the combination of particulate material and oversized material is fed to materials processing equipment or systems. This may be required, for example, to prevent product contamination or prevent interference with the operation of other downstream equipment. In some processes, for example polymer manufacturing, the divided polymer particulate material may be conveyed to metering devices or feed controllers, such as weigh belt devices, screw feeders, or other devices, that are prone to malfunction if oversize materials enter the device. For whatever reason, it is often advantageous to remove oversize material from the divided particulate material, particularly before transferring the material to the metering or feed device. This typically requires the installation of a separate piece of equipment before the metering or feed device to screen out the oversize material.
One such device may be, for example, a vibrating screener wherein the combination of particulate material and oversize material is fed to a screen that is on an incline and vibrating. The particulate material falls through the screen while the oversize material travels over the top of the screen to a disposal port. The screening device can become large, and as in the case of the vibrating screener, may impart vibrations to the supporting structure. The vibrations may interfere with the operations of precision solids metering or feed devices. Furthermore, because these materials handling systems are often gravity feed systems, the installation of a screener may also increase the vertical height of the materials handling system, increasing construction costs and complicating structural designs.
For example, U.S. Pat. No. 4,231,495 discloses a rotary air-lock feeder for a pneumatic conveying line that includes a cylindrical housing with a straight bladed rotor mounted therein to propel materials from an upper inlet to a bottom discharge.
U.S. Pat. No. 4,940,131 discloses a rotary valve having an elevated device for holding a supply of the particulate material, a lower material receiving device and a remote control device. A slide valve disposed in the inlet controls the flow of material therethrough.
U.S. Pat. No. 4,076,150 discloses a rotary air lock having an inlet, an outlet, and adjustable blades to maintain a seal.
U.S. Pat. No. 6,669,411 discloses a rotary air lock feeder having a rotor positioned within a cylinder, and hopper connected with the cylinder through a slotted inlet located in an upper portion of the cylinder.
Other background references include U.S. Pat. Nos. 1,536,124, 2,992,740, 3,151,784, 3,201,007, 4,155,486, 4,164,947, 4,461,700, 4,536,121, 4,635,862, 4,834,783, 4,993,647, 5,725,332, 7,083,069, and 7,112,120.
There exists a need for a device that may remove oversize material without imparting appreciable vibrations to a structure and that does not significantly increase the vertical height of a materials handling system. It would also be advantageous to combine the function of a rotary feeder, for example a rotary air-lock feeder, with the function of removing oversize material from the particulate material into a single piece of equipment that does not produce significant vibration.